Will a preamp help with TV Tuner sensativity....

[Map_guy]

So I am trying to figure out how to pickup the two channels I am missing. I borrowed a friends small digital capable TV to aim the antenna, and with the same antenna and same cable I was able to pull in the two problems channels the samsung TV couldnt. The TV with the weaker tuner is a samsung and the vizio was able to pull the channels in better with no pixilation.

Would a preamp fix this problem?

It would seems the TV signals are getting through to the vizo, just not strong enough for the samsung o lock onto. If it would, any recommendations for a preamp?

Setup is UHF DB-8b and a VHF-Hi combined with a VHF/UHF combiner and a 30' run. My TV fool report....

http://www.tvfool.com/?option=com_wr...1dda7db62b54df

What are the 2 channels you are missing??

[GroundUrMast]

If a tuner has a noisy front-end amplifier or AGC amp, that is, it has a poor noise figure in the traditional, analog sense, then yes I would expect a decent low noise preamp could help.

On the other hand, an ATSC tuner with quiet front end amplification but poor digital equalization capability would get little help from a preamp.

The bottom line, you'll need to try an amp like a CPA-19 or HDP-269.

[Map_guy]

Originally Posted by teleview

What are the 2 channels you are missing??

I was shooting for RF19 (2-1) WGBH and RF20 (5-1) WCVB, for channel 2-1 it will go from 26db to 0.0 db then back to 26db, cutting in and out. Channel 5-1 is just plain touchy to get. The cheaper/smaller vizo pulls in channel 5-1 with ease.

[ADTech]

Your symptom is of multi-path, not a weak signal. It would appear that the Samsung isn't able to cope with the multi-path that is present.

Relocation of the antenna is the usual way to solve this problem. In your case, perhaps a different TV set...

[Map_guy]

Thanks for the reply.

I already ordered a CPA-19, ill see if that helps out. I also grabbed a win tv usb 950q tuner card so I can use a laptop to help locate the antenna. There seems to be an app that shows error received and signal strength. Maybe that will help me get to the bottom of this.

Would a 91xg be a better antenna to cut down on the multi-path?

[ADTech]

It depends upon whether the multi-path is coming from the vertical or the horizontal plane. Both the DB8 and the 91XA have relatively narrow beamwidths in both axes.

[Map_guy]

My wintv usb card came in today and I was able to play with antenna placement. Hauppauge has a signal strength program. There was a lot of signal fluctuation. No real decoding errors, just a +/-3db strength variation.

The usb tuner had no problem with locking onto a signal, but my samsung seems to. A new TV is not an option. The CPA-19 should come in tomorrow and Ill be able to see if that helps, it might since the signal is there just jumping around. Guess that is what I get for an attic placement.

[ADTech]

All the amp will do is amplify the multipath-ridden signal. Unless you get lucky and that happens to shift the signal levels into a more capable spot in the tuner's error correction circuitry, it won't make a difference. All you can do now is keep your fingers crossed and give it a try.

[Map_guy]

One final update....

As wisely predicted. Tried the CP19 and no noticeable difference, still cant get channel 5.1 (WCVB) and channel 2.1 (WGBH) cuts out occasionally with the samsung. The WINTV USB card grabs it no problem.

Curiously; I didn't see any noticeable gain in signal strength from the amp. I did unplug it, the tv stopped getting the signal. So I assume the amp is working? Any way to tell?

And just a final question before I put this project to bed, whats the difference between the CP19 and the CP18?

A new roof may be in my homes future, Ill have the roof guy install the antenna on the roof when that day comes and deal with my limitations until that day. Hopefully that will give me better luck, it would stink to deal with all the wx and wind issues and still not get the channels.

[ADTech]

Unless you are measuring signal POWER (dBm, dBmv, dBuV), you often won't see any difference using the built-in signal meters.

The biggest difference between the PA18 and the CPA19 is that the CPA19 could be used anywhere a pre-amp was needed, including areas with a mix of weak and strong signals due to its excellent overload characteristics. The PA18 should be used in weak signal or fringe areas only. The CPA19 also has a filter that traps out the stuff from around 250 to 400 MHz (public safety, military, taxi, etc) that can cause interference into TV reception systems.

[Map_guy]

Thanks so much for all the help and passing along technical details you cant get any where else. I didnt solve my problem but learned a lot about OTA antennas. GroundUrMast and ADTech are awesome resources to have on this board.